The present invention relates to the manufacture of tires. More particularly, it concerns a process and a machine for the manufacture of a reinforcement for tires.
Tires are generally reinforced by what are currently known as plies, comprising a plurality of adjacent, substantially parallel cords. In crown reinforcements, also known as belts, the cords are generally arranged diagonally with reference to a plane perpendicular to the axis of rotation of the tire. The expression "cord" is to be understood in its most general sense, namely both as a single cord and as a cable formed by the assembling of several individual cords or an equivalent assembly. In the prior art, the most usual method consists in preparing plies whose cords are directed parallel to their greatest length and are coated in rubber from a large number of bobbins of cords which are unwound simultaneously. These plies are then cut at the desired angle into pieces of suitable width, whereupon these pieces of plies are butt-joined by their ends which are parallel to the cords, with or without superimposing of cords, so as to form intermediate or semi-finished products used in the manufacture of the tire proper. The manufacture of such semi-finished products is illustrated, for instance, by U.S. Pat. No. 3,573,135.
This process requires expensive tool equipment and makes it necessary to manufacture a large number of plies which differ in the angles of the cords, the spacing of the cords and the widths of plies made necessary by the architecture of the tires to be produced. For radial carcass tires, the carcass plies are cut at an angle .alpha. of 90.degree. with respect to the plane perpendicular to the axis of rotation of the tire. As to the plies intended to reinforce the crown of the tire, that is to say the part located below the tread, they are prepared in accordance with a considerable number of different angles .alpha., generally, but not necessarily, between 15.degree. and 50.degree..
The prior art also knows other techniques of preparing the crown reinforcement plies in which the reinforcement cords are laid, one after the other, by a reciprocating movement to form a ply of desired width and angle, as described in U.S. Pat. No. 4,409,059. This also implies a relatively complicated apparatus which permits high speeds only with very great difficulty due to the existence of reciprocating movements.